So-called pick point augers are conventionally used in cutting coal and other material, as well as in moving the material so cut back to the machine so that the material can be conveyed away as desired. In conventional auger constructions, the cutting blade, a helical steel ribbon, is welded to a tubular steel shaft. This shaft is, in turn, welded to a mounting flange and the auger assembly is reinforced by means of steel gussets. The mounting flange of the auger assembly is bolted directly to a mating flange on the associated machine.
During a cutting operation, high level noise is radiated from the auger assembly. Further, vibrations are conducted back to the machine where these vibrations are amplified and radiated to the operators as noise. It will be understood that increasing emphasis has been placed on noise control in recent years and, in this regard, permissible noise levels for coal mining have been set forth in the Coal Mine Health and Safety Act of 1969.
Although some work has been done in the field of noise reduction for auger surface noise radiation, auger constructions which have been designed to solve this problem have proven to be structurally inadequate.
More generally, noise radiation is characteristically a problem in digging, cutting, drilling and like machines and solutions have been proposed to solve this problem. Many of these solutions involve the use of a sleeve or collar fabricated of rubber or other resilient material for dampening or otherwise controlling noise. Examples of such constructions are found in U.S. Pat. Nos. 2,997,024 (McLeon); 3,842,942 (Jensen et al); 3,848,931 (Swisher) and 3,926,265 (Bouyoucos). Briefly considering these patents, the McLeon patent discloses a rock drill collar in the form of an inner rubber annulus or sleeve and an outer metal sleeve. The Jensen et al patent discloses a "constrained layer damper and noise suppressor" for a rock drill steel shaft which includes a dampening medium located within a constraint tube. The Swisher patent discloses a drill bit designed to provide vibration attenuation and including a dampening collar comprising a compressible sleeve. The Bouyoucos patent discloses a drill string for a percussive drilling device which includes a resilient member or members used in reducing the level of noise.